Gov. Andrew M. Cuomo delivered a pleasant surprise to skeptical liberal activists last month by tucking a long-discussed plan to provide public financing for state political campaigns into his state budget proposal.

But whether the plan will survive budget negotiations is another question.

On Monday, a national group that seeks to lessen the influence of big campaign donors plans to unveil a $1 million advertising campaign aimed at promoting the public financing plan. The group hopes that the effort will help persuade the governor and lawmakers to keep it in the spending proposal, which must be approved by April 1, as they negotiate in the coming weeks.

The public financing measure is a top priority of government watchdog groups and liberal activists, who see it as a powerful way to diminish the sway of deep-pocketed donors over New York’s government. But Republicans have been firmly opposed to the idea of using public money to pay for state political campaigns, and it is viewed as one of the most vulnerable elements in the governor’s budget proposal.

The commercial uses the restoration of the Statue of Liberty in the 1980s as a metaphor for how a public financing system could remove the corrosive effect of money on New York’s political process, according to supporters. It points out that although the restoration of the Statue of Liberty took several years, the overhaul of campaign fund-raising laws would require only a moment of action.

“The goal of the advertising is to rally the public to support passing comprehensive reform,” said David Donnelly, the executive director of Public Campaign Action Fund. “It’s clear that Albany is broken. Everyone knows what the answers are, and they could just simply pass something in one day.”

Advocates for a public financing system include government reformers, labor unions and the Working Families Party as well as a number of wealthy individuals, including Jonathan Soros, a son of the billionaire financier George Soros. Although they are ultimately seeking to reduce the impact of money on politics, they have spent considerable sums over the past two years promoting their proposal in New York.

In this year’s push, volunteers plan to canvass in key Senate districts, including one in the Bronx and two on Long Island, and supporters are scheduled to gather at the Capitol to lobby for the measure next month.

In his budget, Mr. Cuomo, a Democrat, proposed setting up a public financing system based on the one used in New York City, where individual contributions of up to $175 are matched at a rate of $6 to $1. The public financing measure is part of a package of ethics and campaign fund-raising measures Mr. Cuomo included in his budget in an effort to address a series of recent corruption scandals in Albany.

The proposal pleased activists who had expressed frustration that Mr. Cuomo had not acted more forcefully to promote public financing. But some are now concerned that the governor included the measure as a symbolic gesture, and will not press for its inclusion in the final budget that he negotiates with lawmakers.

Republicans have partial control of the State Senate, and the governor will need their support to pass the spending plan. Scott Reif, a spokesman for the Senate Republicans, said they continued to oppose spending taxpayer money on “the negative television commercials and robocalls people hate.”

In an interview after he introduced his budget, Mr. Cuomo did not sound optimistic about the chances that the public financing plan would be part of the final spending plan. He predicted that it would be an issue in the re-election campaigns of state legislators later this year, but said he wanted to draw attention to the issue in the meantime.